Alloy clad titanium and method of producing same



INVENTOR.

GAll. F. DAVIES AGENT June 14, 1960 G. F. DAvlEs ALLOY CLAD TITANIUM AND METHOD oF PRoDucING SAME Filed Aug. 5, 1954 nited States Piatg-l LLoY cLAn maritim AND Marilou oF PRonUcrNG SAME LGail F. Davies, Willoughby, Ohio, assign'orto Clevte Corporation, Cleveland, Ohio, a corporation oftlhio Filed Aug. `5, 1954, Ser. No. 448,106

Ciaims. (Cl. 2in-132.2)

"This invention relates broadly to a process for the production of a titanium alloy-clad titanium article and to the article of manufacture produced thereby.

-The invention relates more specifically to the novel process for the production of a titanium alloy-clad titanium article` by powder metallurgy techniques.

An important object of this invention is the production of a novel composite article of titanium and a titanium .alloy having therebetween a bond which is highly resistant to shear and tensive separation.

A further object Aof thisinvention is the production of an alloy 'clad relatively light weight titanium article which may be used as armor plate, for rocket nozzle lining, in high wear applications such as gears, impellers, etc., and for chemical apparatus subjected to corrosive atmosphere.

Other objects and advantages will become apparent as' the` description proceeds.

l Referring to the drawing:

'-Figure l is a 'ver-.tical sectional view of apparatus for practicing the invention, viz., a sintering furnace and press showing the positioning of the die and the metal powders therein. Y l

` Figure 2 isla cross-sectional view of an alloy-clad titanium bar according to the present invention showing' the bond between the alloy and the titanium metal.

- Figures 3 and 4 represent a cross-sectional view of a powder charge' prior to applying heat and pressure showing an example of indentations that may be made in theinitial powder layer for altering shear and tensive characteristics of the bond. While unalloyed titanium metal possesses certain Adisalloys of titanium are likewise found to have many valuable properties. In combining a. layer of'titanium' metal with' a layer of an' alloy of titanium in accordance with the'present invention there are found to beadvantages resulting not possessed by either titanium or titatogether in a die to form a composite article of titanium.l

and titanium alloy joined by a bond having a monotonie compositional gradient across its thickness ranging from substantially. unalloyed titanium at one surface to the titanium alloy at the other.

Referring to Figure l, showing one embodiment of the invention, an amount of titanium powder based on .thevfinished thickness of the titanium layer ldesired is placed in a die generally-shown as 3 madeof a Vsuitable .material such as graphite positioned within a furnace 45. tinctive and advantageous metallurgical characteristics;

generallyA shown as 6, having a gas tight vcover 7 and heating means such as a resistance coil 8 surrounding the graphite die. Other conventional heating means may be employed such as a hydrocarbon burner or electrical induction. The resistance coil terminals are connected to terminals outside of the furnace through gas tight insulators 9 and l0; The plunger 2 is connected to an external prime mover by rod 11 which passes through a gas tight gland 12 in top 7. The interior of the furnace may be evacuated through exit 13 by connecting same to a vacuum pump. The titanium charge is leveled and a slight pressure isA applied by plunger 2 to pack the surface and prevent random sifting of one powder into the other. l The plunger is removed from the die and an overlay charge of titanium alloy powder or intimately mixed titanium and allowing metal powders 4 4is introduced and leveled. A vacuum or inert atmosphere isV produced in the die cavity. Heat is applied to the die cavity from an external source and pressure is applied by means of plunger 2. The powders are subjected to a temperature from 600 to l350 C. and pressures from 300 to 150() p.s.i., depending upon lthe alloy used, for a period of time sufficient to eect controlled interdiffusion of the titanium metal and the alloy so as to form a graduated bond whose edges are substantially parallel to the original interface between the titanium and titanium alloy powders; The interdiffusion is found to be in a direction substantially normal to the interface, the extent of interdiusion depending upon the alloy, the temperature, the pressure and the length of time the particular conditions of temperature and pressure are applied. The alloying powder may be in the form of alloy powder, titanium powder coated with alloying metals or a mixtur of titanium and alloying metal powders.

Figure 2 represents a cross-sectional view of a iinished bar showing the titanium metal layer 1 with the titanium `alloy overlaying 4" and graduated bond 5 therebetween.

The term graduated bond -is intended to define the laminar zone of interdifusion intermediate the substantially dient so that no definite line of demarcation exists be,-

tween the titanium alloy, thebond, and the titaniumy metal.

The initial charge of titanium `powder may have indem" tations 14,- Il5 pressed into the `upper surface thereof,l

as illustrated in-'Figures 3 and 4, toproduce a predetermined configuration in -the graduated bond. This may' be designed to moreA evenly distribute shear and tensive stress. -1

`In. someinstances an advantage may be obtained 4by depositing an alloy powder of intermediate composition between the titanium metal powder and the alloy powder overlay. With this technique closer controlover the rate of diffusion may be accomplished.

Alternate vlayers of4 titanium and alloy powders." may be charged into the die to produce a laminated product.'

the titanium metal. l

Where the alloy has a eutectic having a melting point lower than the sintering temperature such that a liquid phase may exist, the alloy powder should be placed below ,the titanium powder to avoid too rapid or spotty penei tration by the alloy as a result of the action of gravity.

A` specific application of this novel process to ther production of titanium alloy clad titanium plate for use as armor comprises using an alloy powder compnismg titanium, 2% iron `and 3% aluminum. The tita- Anium and alloy powders in predetermined amounts are 5 positional gradient in the direction of its thickness, the composition at the respective ends of said gradient conforming substantially to that of the respectively contiguous mass.

8. A composite metal structure according to claim 7 wherein said titanium alloy is a heat resistant titanium ceramet alloy selected from the group consisting of titanium-titanium boride; titanium-titanium carbide; and titanium-titanium silicide.

9. A composite metal structure according to claim 7 wherein said alloy is an aluminum alpha stabilized titanium alloy.

10. A composite metal structure according to claim 7 wherein said alloy is 2% Fe, 3% Al titanium alloy.

1l. A composite metal structure according to claim 7 wherein said alloy is an aluminum gamma stabilized titanium alloy.

12. A composite metal structure according to claim 7 wherein said alloy is a titanium-oxygen alloy.

13. A composite metal structure according to claim 7 wherein said alloy consists essentially of from 25 to 80% titanium carbide and the balance titanium.

, E 14. A composite metal structure according to claim 7 wherein said alloy is a titanium-titanium nitride alloy.

15. The method of producing an alloy clad titanium composite comprising: superimposing separate layers of titanium powder and a titanium alloy powder consisting essentially of powdered titanium and at least one alloy forming element in alloying amounts selected from the group consisting of carbon, boron and silicon; pressing said layers together under a pressure of from about 300 p.s.i. to about 150() p.s.i.; and heating the layers to a temperature of from about 600 C. to about 1350 C. in an inert atmosphere for at least 15 minutes to produce interditusion of metal Ibetween the two layers.

References Cited in the le of this patent UNITED STATES PATENTS 2,491,284 Sears Dec. 13, 1949 2,674,542 Alexander Apr. 6, 1954 2,703,750 Cotter Mar. 8, 1955 

1. THE METHOD OF PRODUCING ALLOY-CLAD TITANIUM COMPRISING: COMPACTING AND SINTERING TOGETHER ALONG AN INTERFACE RESPECTIVE MASSES OF TITANIUM POWDER AND A TITANIUM ALLOY POWDER UNDER A PRESSURE OF FROM ABOUT 300 TO 1500 P.S.I WHILE HEATED TO A TEMPERATURE OF FROM ABOUT 600* TO 1350*C. IN A SUBSTANTIALLY INERT ATMOSPHERE FOR A SUFFICIENT PERIOD OF TIME, NOT LESS THAN 15 MINUTES, TO PRODUCE A BOND BETWEEN SAID MASS COMPRISING A LAMINAR ZONE OF INTERDIFFUSED TITANIUM AND TITANIUM ALLOY AT SAID INTERFACE, SAID ZONE HAVING A UNIFORM COMPOSITIONAL GRADIENT IN ITS THICKNESS DIRECTION RANGING FROM ESSENTIALLY UNALLOYED TITANIUM AT THE SURFACE OF SAID ZONE ADJACENT THE TITANIUM MASS TO SAID TITANIUM ALLOY AT THE OPPOSITE SURFACE OF SAID ZONE. 